热循环对片层石墨/铝复合材料的强度和热导率的影响

Effect of thermal cycling treatment on the strength and thermal conductivity of graphite flakes/Al composites

采用粉末冶金法制备片层石墨增强Al基复合材料(50vol%Gf/6061Al),Gf与Al基体结合紧密,界面处无裂纹、孔洞等缺陷。复合材料在-50~120℃温度范围内分别循环10次、50次、100次和200次,研究不同的循环次数对材料组织和性能的影响。结果表明,循环不同次数时材料的密度没有明显的变化,但随着循环次数的增加,在热应力的作用下Gf发生破裂,材料的强度和热导率均有所下降,当循环次数达到100次时,性能下降速度最快,与未循环样品相比,抗弯强度降低27.4%,热导率下降11.5%。进一步增加循环次数,破碎的Gf和开裂的界面可以有效缓解冷热循环导致的热应力,Gf破坏程度减缓,当循环次数为200次时,与未循环样品相比抗弯强度降低32%,热导率下降13.1%,性能降低趋于平缓。

The graphite flakes reinforced Al matrix composites(50 vol%Gf/6061 Al)were fabricated by powder metallurgy technique.The Gf had a well bonding with Al matrix without cracks and pores.The composites were exposed to a thermal cycling test in the temperature range of-50-120℃.The microstructure and properties of50 vol%Gf/6061 Al were examined when the composites were tested by 10,50,100 and 200 thermal cycles.The density of the composites is almost unchanged under different thermal cycles.With the number of the thermal cycle increasing,the Gf in the composites are cracked due to the stress from the difference of the thermal expansion coefficient between Gf and Al matrix.The strength and thermal conductivity of the composite are decreased with the number of the thermal cycle increasing.After 100 thermal cycles,the bending strength decreases by 27.4%and thermal conductivity decreases by 11.5%compared to that of the sample without thermal cycles.The broken Gf and the cracked interface between Gf and Al matrix could release the thermal stress,therefore,the cracking of the Gf would be retarded.The microstructure and properties of the composites are not serious changed.After 200 thermal cycles,the bending strength decreases by 32%and TC decreases by 13.1%compared to that of the sample without thermal cycles.